Experiments and multiscale modeling of cleavage fracture of AISI 1045steel

Cleavage fracture is a low-energy fracture that propagates along defined low-index crystallographic planes. It usually takes place in metals with body-centered cubic lattice or hexagonal lattice. Cleavage fracture proceeds at multiple sonic speeds, which indicates that no “warning” can be detected and could result in catastrophic failures. Therefore, the safety assessment for cleavage fracture is of great importance. Considering that cleavage failure takes place in various engineering applications, a deep understanding of the cleavage fracture is of crucial importance in fields like material design with desired mechanical properties, safety analysis of engineering structures etc. It is indispensable to comprehensively understand the micro-mechanism of cleavage fracture and then further deduce a macro and micro model to predict when it happens. Different characterization methods and simulation are applied to investigate micro-mechanism of cleavage fracture, as shown in Fig. 1.

The macro-model is based on the classical Orowan cleavage fracture model, enhanced with a stress state dependent strain criterion controlling the micro-defect initiation. It clearly addresses the strain controlled micro-defect initiation stage and the stress controlled crack propagation in the micromechanism of cleavage fracture. In addition to the model formulation, a detailed and reproducible experimental program is proposed in the study to calibrate the model parameters and verify its predictive capability. The implementation procedure of such a model with finite element is simple and it computes fast. Wheras, the model does not take the microstructure information into consideration. To overcome the resistance, the representative microstructure model was applied to link the microstructure features with mechanical properties.